Vitamin D supplements could help obese children and teens control their blood-sugar levels, which could help fend off diabetes, new research shows.

Researchers at the University of Missouri studied 35 pre-diabetic obese children and adolescents who were being treated as part of the university's adolescent diabetic obesity program. They had insufficient or deficient vitamin D levels, similar diets and similar activity levels.

The children and teens were randomly assigned to take either a high-dose vitamin D supplement or a placebo daily for six months.

Those who took the supplement became vitamin D sufficient and lowered the amount of insulin in their blood, the researchers found.

"By increasing vitamin D intake alone, we got a response that was nearly as powerful as what we have seen using a prescription drug," study author Catherine Peterson said. "We saw a decrease in insulin levels, which means better glucose control, despite no changes in body weight, dietary intake or physical activity."